US Patent 7658570 Manhole system

A remotely actuated manhole system is disclosed having a cover that is pivotable relative to a frame secured with a collar on a bulk carrier, the cover being pivotable around a substantially vertical axis between and to open and closed positions. In the closed position covering an opening to a compartment in the bulk carrier, the cover is shiftable vertically between and to locked and unlocked positions by an inflatable seal member below the cover. The manhole system includes catches that prevent over-rotation of the cover from the open position to the closed position, and the catches engage in the locked position by the vertical upward movement of the cover. The inflation of the seal member and the pivoting of the cover are remotely actuated.